Five years ago, large numbers of farmers in central China began falling victim to a mysterious disease marked by high fever, gastrointestinal disorder, and an appalling mortality rate — as high as 30 percent in initial reports. Investigators from the Chinese Center for Disease Control and Prevention hurried to the scene of the outbreak. On the basis of DNA evidence, they quickly concluded that it had been caused by human granulocytic anaplasmosis (HGA) bacteria, which are transmitted by tick bites. Now, however, subsequent studies have shown that this original conclusion was incorrect, and that a previously unknown and dangerous virus has been responsible for seasonal outbreaks of the disease in six of China's most populated provinces. "We expected to find a bacterial infection behaving in an unexpected way — human anaplasmosis has a less than one percent fatality rate in the U.S., and it rarely causes abdominal pain or vomiting or diarrhea," said Dr. Xue-Jie Yu of the University of Texas Medical Branch at Galveston, lead author of a paper on the discovery published online on March 16, 2011, in the New England Journal of Medicine. "Instead, we found an unknown virus." Researchers have named the newly discovered pathogen Severe Fever with Thrombocytopenia Syndrome virus (SFTSV), and placed it in the Bunyaviridae family, along with the hantaviruses and Rift Valley Fever virus. Later investigation has placed its mortality rate at 12 percent, still alarmingly high. Dr. Yu, a specialist in tick-borne bacteria like the species responsible for HGA, first suspected that a virus might be responsible for the outbreaks after close examination of patients' clinical data showed big differences from symptoms produced by HGA, and blood sera drawn from patients revealed no HGA bacteria or HGA antibodies. Dr.
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